It is known to convert the heat into electricity in closed Brayton cycle power plant in which the working fluid is gas.
In one such known closed Brayton cycle power plant cycle 10, as shown in prior art FIG. 1, includes at least one compressor 1 and turbines 2 on a shaft 3, coolers 4, a recuperator 5 and a heater 6 arranged in a closed loop cycle to operate and produce the electricity via a generator 7 (that is also configured on the shaft 3) to transfer to the grid. Such cycle also includes a bypass control arrangement 8 around the compressor and an inventory system 9 arranged in the cycle 10. However, efficiency of the cycle 10 is very sensitive to pressure drop and therefore requires proper attentions while doing so.
During slow power variation in the grid, the grid load variation is compensated by adding or removing gas in the cycle by the inventory system 9. Gas is removed from the closed loop and stored in the inventory system 9 to reduce load. Gas is taken from the inventory system 9 and injected in the closed loop to increase load. By changing gas mass in the closed loop it is possible to change gas density and therefore mass flow i.e. power. However, these changes are slow.
Further, in case of sudden substantive decrease in grid load, the generator 7 is disconnected from the grid. Suddenly, the resistive torque of the generator 7 is removed. But since the inventory system 9 is too slow to reduce the turbine 2 torque, as a consequence, the balance between driving torque from the turbine 2 and resistive torque from the generator 7 is positive, i.e. the shaft line 3 will accelerate and its rotation speed will increase dangerously, which may burst the rotor, if not taken care. Usually in this case, the by-pass control arrangement 8 is opened connecting the compressor discharge to the compressor inlet, which increases the power needed by the compressor 1 (resistive torque) and thus reducing the power unbalance between turbine 2 and generator 7 and compressor 1. The high pressure volume of the cycle 10 is deflated to reach an equilibrium pressure in the cycle thus reducing the driving torque of the turbine 2.
Accordingly, there exists a need for better and fast control of the gas flow to a turbine which eliminates the foregoing disadvantages.